What this MCCB is and what the ratings mean for fit
The Siemens SENTRON 3VA1112-5EF36-0KA0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection, with a continuous current Iu of 125 A and an insulation voltage Ui of 800 V. The interrupting capacity is what decides whether it clears a fault without upstream damage: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at 690 V — so at common 400 V class distribution voltages it handles high available fault current without cascading to the main breaker. The thermal-magnetic release is a TM240, meaning the thermal element is fixed at 125 A and the magnetic pickup is set at 240 A (typical for motor or feeder protection where short-circuit instant trip needs to ride through inrush). The part carries a shunt trip (STL) auxiliary release, order code 3VA9688-0BL33, which lets a remote signal or safety circuit trip the breaker independently of the overcurrent mechanism — useful for emergency-off or interlock schemes. There is no undervoltage release, no auxiliary contact, no ground-fault monitoring, and no communication module, so this is a basic line-protection MCCB with a single remote-trip option.
Thermal derating and operating range
The 125 A rating holds flat from 40 °C to 50 °C, then derates: 120 A at 55 °C, 117.5 A at 60 °C, 115 A at 65 °C, and 112.5 A at 70 °C. If the panel ambient runs above 50 °C, size the load at the derated figure — not the 125 A nameplate. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. Front protection is IP40, so the breaker face is protected against tools and small wires but not against water ingress — mount inside a sealed enclosure for washdown areas.
Panel fit and dimensions
The breaker measures 130 mm high, 76.2 mm wide, and 70 mm deep. The 76.2 mm width (3 inches) is the standard 3-pole MCCB footprint for a 125 A frame — it drops into the same panel cutout as other SENTRON 3VA1 breakers of the same frame size. No rewiring or bus-bar repositioning is needed if replacing a 3VA1112-5EF32-0CA0 or similar 3-pole 125 A variant; the mounting hole pattern and terminal spacing are identical across the frame.